Benzodiazepine (BZ) receptors which are an acting site of anti-anxiety drugs are classified into 2 subtypes of central benzodiazepine receptor (CBR) located on GABA.sub.A receptor/chloride channel complex and MDR located on the central nervous system (glial cells) or adrenal glands (Clin. Neuropharmacol., 16, 401-417 (1993)). Recently, CBR agonists of which representative is diazepam are widely used as anti-anxiety drugs. However, since CBR agonists act directly on GABA.sub.A receptor/chloride channel complex, they cause an anti-anxiety action together with side-effects such as excessive sedation or psychic dependence. On the other hand, since MDR agonists act indirectly on GABA.sub.A receptor/chloride channel complex via synthesis of neurosteroids such as endogenous neuroactive steroids (endogenous anti-anxiety substances), they cause an anti-anxiety action, but do not cause side-effects such as psychic dependence or excessive sedation (J. Pharmacol. Exp. Ther., 267, 462-471, 1993; ibid., 265, 649-656, 1993).
Accordingly, there is a need of the development of therapeutic agents for diseases (obsessive disorders, panic disorders) on which the previous BZs do not have a satisfactorily therapeutic effect, and development of MDR agonists as anti-anxiety drugs which alleviate the side-effects as recognized in the previous BZs.
Furthermore, the compounds which act on MDR, in view of acting on GABA.sub.A receptors, have a possibility of use as therapeutical agents of sleeping disorders, epilepsy, dyskinesia accompanied by muscle rigidity, feeding disorders, circulation disorders, recognition and learning disability or drug dependence (Progress in Neurobiology, 38, 379-395, 1992, ibid., 49, 73-97, 1996; J. Neurochem., 58, 1589-1601; Neuropharmacol., 30, 1435-1440, 1991). In addition, these compounds, in view of the physiological functions of MDR, have a possibility of use as therapeutic agents of cancer (Biochimica et Biophysica Acta, 1241, 453-470, 1995), lipid metabolism abnormality (Eur. J. Pharmacol., 294, 601-607, 1995), schizophrenia (Neuropharmacology, 35, 1075-1079, 1996), cerebral infarction (J. Neurosci., 15, 5263-5274, 1995), AIDS (Abstracts of the fifth international conference on AIDS, p. 458, 1989), Alzheimer's disease (Alzheimer Dis. Assoc. Disotd., 2, 331-336, 1988) or Huntington chorea (Brain Res., 248, 396-401, 1982).
Among the compounds having affinity for MDR, there are indole compounds disclosed in Japanese Translation of PCT publication (Kohyo) No. 6-501030.